1. Field of the Invention
This invention relates to an optical recording medium containing a diacetylene compound and at least one compound selected from the group consisting of auzlenium salt compounds, pyrylium dyes, diene compounds, croconic methine compounds, and polymethine compounds, and to a recording method employing said optical recording medium, particularly to an optical recording medium suitable for optical writing with a radiation and further to an optical recording method by use thereof.
2. Description of the Related Art
Recently, optical discs are of interest among office automations. Since optical discs are capable of recording and storing a large amount of documents and literature in one sheet, documents in an office can be pigeonholed or managed with good efficiency. Various recording media have been investigated for such an optical disc, and those utilizing organic materials are attracting attention because of low price and ease in manufacture.
As such an organic material for recording medium, a diacetylene compound has been known and a recording technique employing said compound for a laser recording medium by utilizing the thermal color change property of said compound is disclosed in Japanese Laid-open Patent Publication No. 14780/1981. However, in this specification, there is no description about what kind of laser has been employed or has to be used, but there is only a description that recording was performed by use of a laser.
The present inventors have investigated about laser recording of the diacetylene compound by use of various kinds of laser and consequently confirmed that, while thermal color change recording may be feasible by use of a large scale and high output laser such as argon laser, etc., no laser recording is practicable when a semiconductor laser of small model and relatively low output (wavelength: 800 to 850 nm) was used. However, a practical recording medium of an optical disc, etc. is desired to have a capability of optical writing with a semiconductor laser of small size and low output.
Further, the recording layer of the prior art comprising the diacetylene compound as described above is formed by use of fine crystalline powder of the diacetylene compound, and hence the molecules of the diacetylene compound are randomly oriented within the recording layer, whereby such inconveniences may be caused that light transmittance or reflectivity may vary the degree of the chemical reactions may vary depending on the position on the medium. Thus, it cannot necessarily be suitable for high density recording of good quality.